1. Field of the Invention:
This invention relates to a medicinal use of .alpha.,.beta.-unsaturated fatty acids, more particularly to a medicinal composition containing .alpha.,.beta.-unsaturated higher fatty acids, and to a method for treating diabetes or improving lipid metabolism by the administration of said composition to a human being, and to a process for separating said compounds from freshwater clam by extraction.
2. Description of the Prior Art:
Freshwater clams such as Corbicula sandai belonging to Corbiculidae have long been believed to be effective for treating liver disease, and various studies have been made on the pharmaceutical effectiveness of freshwater clams.
For example, thoracic duct lymph-accelerating effect, liver function-enhancing effect, bile acid secretion-increasing effect, etc. of a freshwater clam extract have been reported. Further, effective ingredients contained in freshwater clams showing the above-described pharmacological effects have been studied as well, and some reports say that amino acids such as methionine, cystine, cystinic acid, etc. are responsible for liver function-enhancing effect.
However, ingredients obtained by extraction of freshwater clams have not been studied with a view toward improving lipid metabolism. This may be attributed to the consideration that shellfish including clams are usually rich in choresterol,
Also, such ingredients have not been studied as possible therapeutic agents for diabetes.
Under such circumstances, the inventors of the present invention have examined the pharmacological effects of substances which are obtained by extracting the whole part of freshwater clams with hot water, concentrating the water extract and extracting it with an aprotic solvent, and which are obtained by drying the fleshy part isolated after said extraction with hot water and then extracting the dried fleshy part with an aprotic solvent. It has been found that said substances possess the effect of improving lipid metabolism (prophylaxis and remedy of hyperlipemia, lipotropic effect, and propylaxis of arteriosclerosis), and the effect for curing diabetes. As a result of further investigations, the inventors have isolated specific four specific .alpha.,.beta.-unsaturated higher fatty acids from the above-described substance and have concluded that they are the ingredients responsible for the above-described pharmacological effects, thus having achieved the present invention.